Author: Volker Böhm
Date: 01:14:30 08/28/04
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Hi Stuart, as everytime there is no "right" or "false" for nullmove condition. It depends on your chess engine. I have the following conditions, the nullmove is not done if: 1. Nullmove has been done right before 2. hash entry says the value is < beta (I use even hash entries if remaining_depth <= hash_remaining_depth + 3) to thest this condition - it didn´t work for a long time, hazardous it works now - This is a "poor-man´s" verified nullmove :-) 3. Remaining Depth <= 1 4. Material + Pawn < Beta (eval + Pawn < Beta works less good for spike - seems material is a more stable condition than positional value if not moving 5. King is in Check 6. Beta <= MaxVal - Ply (Beta says player to move is forced mate in the next ply) 7. If player to move can mate in one move (have a static test that finds ca. 95% conditions) 8. King has been in Check in ply - 2 and ply - 4 (idea from gnu-chess I don´t know if it is worth something - not enough tests) 9. Not if player to move has no range piece (queen, rook, bishop) 10. Not if root-search-depth is below 3 Greetings Volker
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